Requirement of casein kinase 2 for entry into and progression through early phases of the cell cycle.

Abstract

Requirement of protein kinase CK2 during cell cycle was examined by specific perturbation of CK2 in the intact cell by antisense-oligodeoxynucleotides and microinjection of antibodies. When quiescent human primary lung fibroblasts (IMR-90) were exposed before growth stimulation to oligodeoxynucleotides complementary to the translation start region of mRNAs encoding subunit alpha or beta, a significant inhibition of growth stimulation by epidermal growth factor or serum was observed. The inhibition was reversible and decreased or abolished with mutated antisense-oligodeoxynucleotides. The inhibitory effect coincided with a decrease of CK2 protein (immunostaining with beta subunit antibody) at entry into and during the first several hours of the cell cycle. Injection of beta-specific monoclonal and polyclonal antibodies into IMR-90 cells caused significant inhibition of growth stimulation. The inhibition was reversible, not observed with control antibodies, and strongly reduced by coinjection of CK2 holoenzyme. Cytoplasmic injection inhibited up to 50-60% and was effective at two intervals within the first 2 h and at 12-16 h poststimulation, i.e., at G0/G1 phase transition and at G1/S boundary, respectively. The inhibition at G0/G1 transition is paralleled by an inhibition of cytoplasmic-nuclear translocation of beta subunit protein. Injection of beta antibodies into the nucleus inhibited growth stimulation by as much as 80-85% and was effective for the first 6 h poststimulation, i.e., at G0/G1 phase transition and progression through the adjoining early G1 phase. Nuclear as well as cytoplasmic injections performed during S phase affected neither DNA synthesis nor cell division.(ABSTRACT TRUNCATED AT 250 WORDS)